Butter a 9x9 inch pan and set aside.
In a heavy 2 quart saucepan, combine the syrup, sugar and vinegar. Bring to a boil over medium heat, stirring constantly until sugar dissolves. Continue cooking without stirring until a candy thermometer reads 300 degrees F (150 degrees C).
Remove from heat and quickly stir in the soda; mix well. I
Immediately pour candy into prepared pan, Do not spread. Cool and break into pieces.